Now to a riveting allegations about flight 800, that mysterious crash years ago which killed 230 people. Tonight former investigators are speaking out for the first time saying the fbi covered up what really happened. These whistle blowers believe the plane was taken down by a missile and they want a new investigation. Brian ross takes a close look at these disturbing charges. Reporter: Today's allegations only add to the mystery that won't go away. Since that hot july night r 17 years ago when two flight 800 blew up over long island sound, spreading burning debris for miles. The investigation took four years, including the painstaking reconstruction of the 747 aircraft, but now six people involved in that investigation are coming forward to claim the government has been trying to cover up the really reason the plane crashed. Reporter: Hank hughes is a retired safety boar investigator. It was either a terrorist attack that they wanted to ignore or an accident as a result of a military operation that went wrong. Reporter: But the fbi and the national transportation safety board concluded the plane was brought down by a faulty fuel tank, not an act of terrorism or military accident. We have no evidence of a bomb, a missile, a criminal act. Reporter: But now the soon to be released documentary film, including what it says is a new analysis of radar images supposedly showing an object closing in on the plane, is giving new attention to a series of old theories that there was doesn't it seem hard to imagine that the us government would try to hide a terrorist attack on an american plane? It's hard to imagine, but governments are capable of doing some terrible things. Reporter: The families of some of the 240 victims say the film is exploiting their pain, and a former senior investigator told abc news the allegations of a cover up are absurd. I find that ridiculous quite frankly. Reporter: And ignores serious, solid evidence. Everything I've heard so far is just a rehashing of old speculations, if you will, that don't match the facts of the investigation. Reporter: The former investigators today petition the ntsb to re-open the investigation into the case. The director said today it was a thorough investigation then but if there is anything new to consider, the board will do so. They're alleging allegations of a coverup to the white house. I was working at the white house then in the situation room meetings with the ntsb or the fbi never any hint of any kind of a coverup that I saw or heard. Do you know why they're coming forward now? The new film is out and they're trying to promote the film.

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